1. Field of the Invention
This invention relates to the field of enclosures and more specifically, to electromagnetic interference shielding enclosures.
2. Prior Art
In the manufacture of computers and computer related equipment, enclosures are provided as containers for such devices. These enclosures come in different shapes, sizes and materials, but normally most enclosures have a removable cover. Typically, the component parts of the equipment are mounted into the base portion of an enclosure and then the cover is placed to seal the equipment within. However, where electronic and computer components, such as circuit boards, semiconductor chips, memory devices, etc., are involved, it is necessary to seal in the electromagnetic radiation generated by these internal devices, as well as protecting these devices from external electromagnetic radiation. The purpose for this isolation is to provide shielding from electromagnetic interference (EMI).
EMI shielding is provided by using an electrically conducting material which surrounds the device to be shielded. When separate sections are assembled to form an enclosure, a seam formed at the juncture of the sections must also inhibit leakage of EMI radiation. Significant leakage problems are typically encountered at this seam.
Prior art enclosures have used conducting materials such as copper, beryllium-copper, conductive rubber, etc., as seam materials. However, these materials were utilized primarily to provide a gasket to inhibit radiation leakage. Gaskets provided effective seals when enclosures were initially assembled, but lost their effectiveness as an EMI shield with repeated use. Therefore, it was recommended that these prior art gaskets be replaced each time an enclosure was opened and resealed. This requirement placed additional constraints, as well as cost, whenever such enclosures were opened for maintenance and repair.
If the gaskets were not replaced, the shielding effectiveness of the seam eroded further with each opening and closing of the enclosure. Further, prior art gaskets had a potential of being positioned improperly, thereby preventing the formation of an effective shield at the seam.
It is appreciated then, that a novel type of EMI shielding seam is needed to provide a seal for an enclosure, wherein such seal may be used repeatedly for subsequent openings.